Valves are commonly used in process control systems to control the flow of process fluids. Rotary valves (e.g., butterfly valves) typically have a closure member (e.g., a disc) disposed in a fluid path. A shaft operatively couples the closure member to an actuator that rotates the closure member between an open position and a closed position to allow or restrict fluid flow between an inlet and an outlet of the valve. When the closure member is rotated to the closed position, the closure member sealingly engages a valve seat or sealing surface (e.g., a seal ring fixed to the valve body) to restrict fluid flow through the valve.
To couple the valve shaft and the closure member, a hole or aperture is typically formed in a portion of the closure member parallel to a face of the closure member. At least one fastener (e.g., a pin) is employed to couple the valve shaft and the closure member. In particular, the fastener may be disposed in the aperture of the closure member and a coaxially aligned aperture of the valve shaft to couple the valve shaft and the closure member.
However, in relatively larger valves such as valves having diameters greater than 12 inches, it may be impractical to form (e.g., via a drill) an aperture (e.g., a blind hole) that is parallel to the face of the closure member. Instead, the aperture is typically formed substantially perpendicular to the face of the closure member and the fastener, which is disposed in the aperture, couples the valve shaft and the closure member. However, such a connection or coupling may exhibit lost motion between the valve shaft and the closure member because the fastener may back out of the aperture due to valve vibrations during operation. Thus, such a connection often requires permanent attachment (e.g., via welding) of the fastener to the valve shaft and/or the closure member.